ULTRACENTRIFUGAL ANALYSIS OF YOLK PROTEINS IN RAINBOW TROUT EGG AND THEIR CHANGES DURING DEVELOPMENT

Abstract

Yolk proteins in Salmo irideus (rainbow trout) eggs were studied by means of ultracentrifugal analysis, and the following facts were clarified. Unfertilized eggs contain two protein components, designated as component I (90% in relative content) and component II (10%). The sedimentation constant for component I is 9.4 S and its molecular weight is approximately 240,000 ~ 260,000. The phosphorus and lipid contents of this major component are similar to those of a lipovitellin in hen's egg yolk, but the molecular weight is considerably smaller than that of the hen's lipovitellin. Component I is split by alkali into two subunits. The sedimentation coefficient for the subunits is 4.9 S and the molecular weight is approximately 120,000. The sedimentation coefficient for component II is 3.1 S, and the phosphorus content is higher than that of component I but is lower than that of hen's phosvitin. A new component of 11.2 S appears at the beginning of the eyed stage, and is inferred to be a protein in the blood formed at this stage. The relative changes of these three components during the synchronous development of embryo from fertilization to the swim-up fry stage were followed.